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Math Help - basic maths question

  1. #1
    obi
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    basic maths question

    We're doing some school holidays maths. Son is 8 yo.

    I don't understand the technique for this question..

    these 6 numbers can be arr in 3 pairs so they add up to same answer

    158 235 318 426 349 266

    I've done it the hard way, but im there is a technique here.
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  2. #2
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    Quote Originally Posted by obi View Post
    We're doing some school holidays maths. Son is 8 yo.

    I don't understand the technique for this question..

    these 6 numbers can be arr in 3 pairs so they add up to same answer

    158 235 318 426 349 266

    I've done it the hard way, but im there is a technique here.
    I do not thing there is an easy way unless guessing which work and do not.
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  3. #3
    obi
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    if this is true then this is too hard for an 8yo. There MUST be a way to work this out. Guessing could take all day.


    Quote Originally Posted by ThePerfectHacker View Post
    I do not thing there is an easy way unless guessing which work and do not.
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  4. #4
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    Quote Originally Posted by obi View Post
    We're doing some school holidays maths. Son is 8 yo.

    I don't understand the technique for this question..

    these 6 numbers can be arr in 3 pairs so they add up to same answer

    158 235 318 426 349 266

    I've done it the hard way, but im there is a technique here.
    This is for your 8-yr old son? If so, then let's think like we are 8 years old too, meaning we do not know hard Math yet. We are into addition/subtraction yet mostly.

    A pair is two.
    So if the sum of the units digit of a pair ends up as the same for all 3 pairs, then we might get the same sum for the 3 pairs?

    The six units digits are 8, 5, 8, 6, 9, 6.
    Adding any two that might give the same last number, or the sum's units digit, might solve the problem.
    6+8 = 14, and 5+9 = 14.
    The units digit of both sums is same 4. Umm, maybe good.

    Then,
    235 +349 = 584
    158 +426 = 584
    318 +266 = 584

    Three pairs, same sum. Good.

    ------------------
    An exercise for sudoku puzzles.
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  5. #5
    obi
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    i don't understand. If I don't understand how can an 8 yo?

    What is this <sum of the units digit> ?
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  6. #6
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    Quote Originally Posted by obi View Post
    We're doing some school holidays maths. Son is 8 yo.

    I don't understand the technique for this question..

    these 6 numbers can be arr in 3 pairs so they add up to same answer

    158 235 318 426 349 266

    I've done it the hard way, but im there is a technique here.
    Another way, although I doubt if an 8-yr old knows the reasoning behind it yet.

    There are 6 given numbers to be divided into 3 pairs. Each pair adds up to the same number.

    So, add the 6 given numbers, and divide the total by 3 to get that "same number" sum of any pair.
    158 +235 +318 +426 +349 +266 = 1752
    1752/3 = 584
    So any pair should add up to 584.

    What is the number to add to 158 to get 584?
    Why, subtract 158 from 584, of course.
    So, 584 - 158 = 426. Hey!
    Hence one pair is 158 and 426.

    Go get the other two pairs.
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  7. #7
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    Quote Originally Posted by obi View Post
    i don't understand. If I don't understand how can an 8 yo?

    What is this <sum of the units digit> ?
    I see.

    Okay. In 235, the last number, the 5, is the units digit.
    (the first number, the 2, is the hunhreds digit; the 3 is the tens digit)
    (Hundreds digit, tens digit, units digit -----for a number with 3 digits. May I assume your son understands a digit?)

    So "sum of the units digits" of "235 +349" is 5+9. Which is 14. Then the units digit of this 14 is 4.
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  8. #8
    obi
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    thank you.

    we got this maths from a book for year 4 students. I find it's too advanced for an 8 yo.
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  9. #9
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    Quote Originally Posted by obi View Post
    thank you.

    we got this maths from a book for year 4 students. I find it's too advanced for an 8 yo.
    I see again. I see he is not yet a Year-4 student.

    Pushing the son too early?
    Is he a gifted one, though?

    Advice, if your son's got a "normal" Math-brain, and he is just in 2nd Grade yet, please avoid 4th-Grade Math for now for the kid. Drill him on his current Grade level only.

    If he is gifted, hey, persevere on those 4th-Grade Math exercise!
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  10. #10
    obi
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    he is going into year 4 from year 3 last year.

    he is just a normal brain!
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  11. #11
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    Quote Originally Posted by obi View Post
    he is going into year 4 from year 3 last year.

    he is just a normal brain!
    Oh, I see again.

    Then good luck to him. Be patient. With you there helping him, he will learn.

    Happy New Year!
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  12. #12
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    Quote Originally Posted by obi View Post
    he is just a normal brain!
    As a parent of six, I know from experience, never tell him yet. He needs to know that he is talented. When he reaches the right age he is going to know he is average.
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  13. #13
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    I don't think anyone has said this; forgive me if they have.

    Isn't it a case of just being able to put the numbers in order? Put them in order, and then take the biggest and the smallest and pair them up. Then the next biggest and the next smallest... There is no need to do any adding or even know what the totals are.
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  14. #14
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    Quote Originally Posted by TheBrain View Post
    I don't think anyone has said this; forgive me if they have.

    Isn't it a case of just being able to put the numbers in order? Put them in order, and then take the biggest and the smallest and pair them up. Then the next biggest and the next smallest... There is no need to do any adding or even know what the totals are.
    Umm, just asking, if you don't do any adding, how will you know the sums are the same?
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  15. #15
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    Well they just have to be. If you're told that the numbers will pair up, then the smallest one has to go with the largest and so on. If the largest one went with anything other than the smallest, then there wouldn't be a number to go with the smallest one to make it add up.
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